The invention relates to a mobile radio terminal.
To be more precise, the expression xe2x80x9cmobile radio terminalxe2x80x9d means a cordless telephone terminal or a GSM mobile terminal, but this definition is not limiting on the invention.
The invention applies more particularly to mobile radio terminals which provide all three of the earpiece, loudspeaker, and ringer functions, and which guarantee compliance with safety rules imposed to protect the user.
The safety rules specify in particular that the level of the ringing signal must not exceed a predetermined threshold when the user""s ear is near the means providing the ringer function (acoustic shock). Paradoxically, the ringing level must be amplified when the terminal is not near the user""s ear so that the user can hear the ringing signal. The same applies to the voice signal when the terminal is being used in loudspeaker mode.
To this end a GSM mobile radio terminal usually incorporates an audio transducer to provide the earpiece and loudspeaker functions and a component such as a ringer or vibrator separate from the transducer to provide the ringer function. The ringer or vibrator is sited away from the transducer to prevent acoustic shock. However, its presence significantly increases the overall size of the terminal and leads to a non-negligible increase in the unit cost of the terminal.
Also, this does not solve the loudspeaker problem.
U.S. Pat. No. 4,504,701 describes a cordless telephone terminal including a ringing signal processor circuit and an audio amplifier connected to a receiver emitting a voice signal and a ringing signal. To protect the user from acoustic shock, the terminal further includes a gravity switch connected in parallel with an attenuator resistor between the ringing signal processor circuit and the amplifier. When the terminal is on its base, or out of its base but in a substantially horizontal position, the gravity switch is in a predetermined position in which the ringing signal is transmitted to the amplifier and thus to the receiver without modifying it. When the terminal is removed from its base and is in a substantially vertical position the switch is in the open position so that the ringing signal is attenuated by the parallel resistor to a predetermined level preventing acoustic shock. The attenuated signal is transmitted to the transducer via the amplifier.
In other words, the ringing signal is unmodified when the terminal is on its base or off its base but in a horizontal position, while it is attenuated when the terminal is not on its base and is in a vertical position, as it may well be when it is near the user""s ear.
However, the ringing level is adjusted according to the position of the terminal, which does not allow for the position of the user.
The terminal may be in a vertical position without being on its base in situations other than when it is near the user""s ear, for example when it is placed on a table. The ringing signal is then attenuated even though the terminal is not near the user and as a result the user may not hear it ringing.
Conversely, the terminal can be in a horizontal position and also near the user""s ear, for example if the user is lying down.
For the same reasons, a gravity switch in parallel with a resistor cannot be effectively applied to mobile terminals which are often in a vertical position at a distance from the user, in a bag, a pocket or the like.
Also, the device described in the above document provides no means of adjusting the loudspeaker output signal.
Finally, the above device requires additional components, such as the resistor and the switch, which add to the overall size and the cost of the terminal.
Document WO 94/13065 relates to a device for adapting the level of a voice signal to suit the position of the terminal, which is either a hands-free position or a conventional listening position. To this end the device includes switches which set the voice signal to a first level, for example a low level, if the position is the conventional listening position or a second level, for example a high level, if the position is a hands-free position.
The document addresses the problem of acoustic shock. However, the means for solving the problem have the drawback that they are electromechanical, and therefore bulky, and require a terminal to be provided with a flap for defining the hands-free and conventional listening positions.
Document EP 0 171 065 concerns an acoustic feedback device for a loudspeaker. The idea is to place a microphone on the loudspeaker diaphragm in order to regulate the output level of the loudspeaker, i.e. to maintain it as constant as possible. The objective is in fact to improve prior art regulator devices in which the microphone faces the loudspeaker but is at a distance from it.
Consequently, the problem addressed by that second document is the exact opposite of that addressed by this application, which is how to modify the level according to certain parameters.
The object of the invention is therefore to alleviate the above drawbacks.
The invention consists in a cordless or mobile telephone terminal generating a ringing signal or a voice signal at a level which prevents acoustic shock.
The invention also concerns a compact low-cost mobile radio terminal.
To this end, the invention proposes a mobile radio terminal including an audio transducer providing earpiece and loudspeaker functions and an outlet of which is oriented towards the front face of the terminal, characterized in that the audio transducer additionally provides a ringer function and in that the terminal further includes, coupled to the transducer, means for adjusting the level of the sound wave emitted by the transducer in a main direction substantially perpendicular to the front face, the adjustment being effected regardless of the position of the terminal relative to a user and so that said level is sufficient for distant use of the terminal and less than a predetermined value for close use.
In a first embodiment of the terminal the adjustment means include:
means for measuring a parameter representative of the degree of masking of the transducer, and
means for determining the level of the sound wave that the transducer must produce given the measurement effected by the measuring means.
In a first variant the means for measuring a parameter representative of the degree of masking of the transducer comprise means for measuring the attenuation of background noise picked up by the microphone of the terminal.
In a second variant the means for measuring a parameter representative of the degree of masking of the transducer comprise means for measuring the impedance of the transducer.
In a second embodiment of the terminal the adjustment means include a guide member for the sound wave comprising a guide wall in which at least one guide hole is formed, the guide member being rigidly coupled to the front face of the terminal so that the guide hole faces the outlet of the transducer to limit the level of the sound wave emitted in the main direction and the guide wall and the front face of the terminal form a diversion channel for at least part of the sound wave in a secondary direction different to the main direction.
In a third embodiment of the invention the adjustment means include:
a flap in which the transducer is mounted and which is coupled to the front face of the terminal and mobile between an active position in which it bears against the front face and an inactive position in which it does not bear against the front face,
means for detecting passage from the inactive position to the active position and vice-versa, and
means for producing a signal for adjusting the level of the sound wave from the transducer according to the position of the flap.
The invention also proposes a method of adjusting the level of a sound wave produced by a transducer mounted in a mobile radio terminal as previously described, characterized in that the adjustment is effected in a main direction substantially perpendicular to the front face of the terminal and regardless of the position of the terminal relative to a user.
In a first implementation of the method the adjustment is effected in accordance with the degree of masking of the transducer.
To this end it comprises the steps of:
measuring a parameter representative of the degree of masking of the transducer, and
adjusting the level of the sound wave that the transducer must provide accordingly.
In a second implementation of the method the adjustment is effected by diverting at least part of the sound wave in a secondary direction different from the main direction.
In a third implementation of the method the adjustment is effected by detecting a pressure difference applied to the front face of the terminal.